Seminal Extracellular Vesicles LGALS3BP as a Potential Biomarker of Varicocele‐Associated Infertility in TMT‐Based Quantitative Proteomic Analysis

The proteomic analysis of seminal plasma (SP) is a powerful tool for screening and identifying potential novel biomarkers of male infertility. However, the proteomic composition of seminal extracellular (SE) vesicles in varicocele (VC) is still poorly characterized. The main objective of the present study was to compare the proteome of SEs between infertile men with VC and fertile men without VC and to reveal differentially expressed SEs proteins (DESEPs) that can serve as potential novel biomarkers of VC‐associated infertility. SEs were isolated and purified from SP, and SEs proteins were extracted and labeled with TMT and analyzed by high‐resolution LC‐MS/MS. A total of 1457 proteins were quantitatively identified in these SEs samples. Of these proteins, 175 DESEPs (76 upregulated and 99 downregulated) were identified. Bioinformatics analysis indicated that the molecular functions and biological processes of these DESEPs were involved in metabolism, cell growth and/or maintenance, energy pathways, transport, and cell activation. Among these DESEPs of interest, PGK2 and LGALS3BP were validated by Western blotting. The expression level of the SEs LGALS3BP was also determined by ELISA. A significant positive association was observed between the concentration of SEs LGALS3BP and clinical characteristics. Moreover, receiver operating characteristic (ROC) curve analysis showed that SEs LGALS3BP had better predictive efficacy than seminal LGALS3BP as a potential diagnostic biomarker of VC‐associated infertility. Differences in the SEs protein profiles indicate that DESEPs may serve as potential biomarkers for VC‐associated infertility.